1. Field of the Invention
The present invention relates to well devices employed in the completion and production of oil and gas wells. More specifically, the invention relates to a well tubing hanger which is retrievably anchored in a subsurface location within a well casing or other well conduit and to a cooperating concentric tubing anchor used to anchor a tubing string extending from the well surface within the tubing hanger.
2. Description of the Prior Art
Anchor-seal assemblies of various types have been used in the past in well working operations, and in the production of a well. For instance, seal assemblies in the form of packers are known for isolating formations for treatment, or for isolating segments of liners or well casings. Packers are routinely used for sealing production strings to well liners or well casings to define flow paths from producing formations to the well surface.
Particularly in the case of packers, the seal assembly is usually positioned within a well by means of a pipe string, and then set in sealing and anchoring engagement with the surrounding conduit. The setting operation usually involves the movement of multiple components of the packer to expand one or more resilient seal members, and to wedge anchoring slips against the surrounding well conduit or casing.
In spite of advances in the art, a need exists for a pack-off well apparatus which is adapted for specific, demanding environments. For example, in gas injection operations, a tubing hanger is needed which is capable of anchoring and sealing a well tubing string in a borehole, the tubing hanger having an extremely high axial load capability.
A need also exists for such a pack-off apparatus which can be used for gas injection operations where temperature changes subject the apparatus to large static loads.
A need also exists for such an apparatus which can serve as a redundant wellhead when set at a shallow depth in a borehole.
It is an object of the present invention to provide a tubing hanger with an axial load capability which is substantially equivalent to the load capability of the tubing string supported by the tubing hanger.
Another object of the invention is to provide a tubing hanger adapted for gas injection processes which can be set at a shallow depth below the well surface and which can tolerate the large static loads encountered due to temperature requirements encountered during such operations.
Another object of the invention is to provide such a tubing hanger which cannot be inadvertently pulled from the anchored location in the well casing by an impact to the upstream equipment located at the well surface such as might occur if an ocean vessel inadvertently rammed the surface structures.
Another object is to provide a tubing hanger which eliminates flow ports in the production tubing or work string, or a component in direct fluid communication therewith, to provide actuating fluid from the bore of the production tubing to well tools to initiate desired operations, such as the setting of the packing element. Seals employed with such ports must be sealed in subsequent operations and are subject to deterioration and hence leakage.
Additional objects, features and advantages will be apparent in the written description which follows.